The invention relates to a substrate treatment process, in which substrates are moved by means of a transporting device in a transporting direction through a substrate treatment installation consisting of a number of chambers, the substrates being moved by way of transporting sections of the transporting device that are driven independently of one another and the transporting sections of the transporting device being driven in such a way that, if they dwell temporarily in the transporting section, substrates arranged on them are moved back and forth.
A substrate treatment process should be understood here as meaning in particular a process for applying and/or removing a surface layer of a substrate, in particular a substrate in sheet form, for example a plate of glass or the like, in which the substrate is heated by a substrate treatment device, for example a coating device, dry-etching device or the like, or/and by a heating device additionally arranged in a substrate treatment installation.
In dependence on the substrate treatment process to be realized in the substrate treatment installation, the substrate to be treated is exposed to differing process temperatures and temperature regimes in different chambers of a substrate treatment installation. The temperatures that the substrates assume are of decisive importance for the quality of the result of the treatment.
It is known that substrates that are treated in a continuous vacuum coating installation are moved through the vacuum coating installation in a transporting direction that lies in the longitudinal extent of the substrates. This vacuum coating installation likewise has in a longitudinal extent that lies in the transporting direction a number of functional chambers. For example, the vacuum coating installations are designed as 3-chamber installations or as 5-chamber installations.
A 3-chamber installation consists of                a first functional chamber, to be specific the entry lock, which also represents one physical chamber of the installation,        a second functional chamber, often consisting of a number of physical chambers of the installation, to be specific                    a first transfer chamber (in one physical chamber of the installation),            a process chamber (usually in a number of physical chambers of the installation) and            a second transfer chamber (in one physical chamber of the installation), and                        a third (functional) chamber, to be specific the exit lock, which in turn represents one physical chamber of the installation.        
A 5-chamber installation consists of                a first functional chamber, to be specific the entry lock, which also represents one physical chamber of the installation,        a second functional chamber, to be specific a first buffer chamber, which also represents one physical chamber of the installation,        a third functional chamber, consisting of a number of physical chambers of the installation, to be specific                    a first transfer chamber (in one physical chamber of the installation),            a process chamber (usually in a number of physical chambers of the installation) and            a second transfer chamber (in one physical chamber of the installation),                        a fourth functional chamber, to be specific a second buffer chamber, which also represents one physical chamber of the installation, and        a fifth (functional) chamber, to be specific the exit lock, which in turn represents one physical chamber of the installation.        
In the individual chambers, the substrates are exposed to differing inputs of heat. Depending on whether a heating-up or just a transfer of the substrate to the next process chamber or a controlled cooling-down is intended in the respective chamber, a positive or negative input of heat is concerned. If the substrate is heated by heaters, which are for example arranged between transporting rollers of the transporting device, there is a positive input of heat. If, on the other hand, in the case of a non-heated chamber, heat is dissipated from the substrate into the chamber by way of the transporting rollers or by heat conduction or heat radiation, there is a negative input of heat.
In a 5-chamber installation, a substrate is for example heated up to a temperature of about 200° C. upstream of the process chamber in the transporting direction. In this case it is known to arrange a number of heaters lying one behind the other in the transporting direction between the transporting rollers of the transporting device. In this case, each heater brings about an input of heat of its own to the substrate.
With these active heating measures, the substrates can become very intensely heated and there is the problem that differingly hot zones form in the chambers. During normal operation, that does not present a problem, since the substrates are moved continuously through the substrate treatment installation and a dynamic energy balance is thus established. As a result, there is what is known as a smoothing of the temperature profile on the substrate that forms in a chamber.
At the moment that the transporting device that brings about the movement of the substrates suddenly comes to a standstill, for example when there is a backup of substrates, the situation changes fundamentally. Typically, in such a case all heat sources, that is to say heating devices, or else all substrate treatment devices, such as coating or etching devices, must be switched off immediately and the transporting of the substrates stopped. On account of the resultant standstill of the substrates, there is no longer any smoothing of the temperature profile that forms on the substrate. I.e. parts of the substrate that are located on a hot region at the time of the standstill, for example directly over a heater, are heated up further in an uncontrolled manner. This is even the case when the heat sources are switched off, because both the heat sources and other, likewise heated-up components of the installation continue to radiate heat. The dynamic energy balance is disturbed. This situation leads to thermal stresses in the substrates, as a consequence of which they may bend or even break.
DE 10 2010 043804 A1 describes for example a process that serves for limiting damage in the event of a fault occurring, a process in which, if there is a malfunction, the substrate is moved back and forth in one section of the transporting device over a length of the substrate, in order to achieve a homogenization of the temperature in the substrates.
However, it may also be the case that it is predetermined in a process sequence for the treatment of a substrate that a substrate must dwell longer in a chamber, in order for example to shorten cycle times or in cases in which irregularities occur during cyclical operation, for example when there are gaps between substrates. If no allowance is made for such cases, and there is no appropriate response to them, there may be instances of bending of the substrate to the extent that it breaks, necessitating long times to restore the situation. However, when there is dwelling in a chamber, it is also necessary to compensate for a heat profile, for example a heat profile that occurs periodically over the length of the chamber, is brought about in particular by an arrangement of a number of heaters lying one behind the other in the transporting direction between the transporting rollers of the transporting device and would lead to a periodic temperature profile over the length of the substrate in the transporting direction. This is so because, even if such a temperature profile would not lead to glass breakage or the like, the temperature profile would be imposed on the substrate and would not be compensated quickly enough in downstream treatment steps, and would consequently lead to variations in quality in downstream treatment steps. It could thus happen for example that downstream coating operations would produce layers with a streaky appearance.
There is therefore the need for an improved substrate treatment process to reduce differing inputs of heat that bring about stresses on the substrate as a result of both process-induced and malfunction-induced dwell times of the substrate in a chamber of the substrate treatment installation.